1. Field of the Invention
The present invention relates to a liquid jetting apparatus provided with a plurality of head units.
2. Description of the Related Art
In the field of a liquid jetting apparatus, there is known a liquid jetting apparatus configured so that a plurality of head units, each of which includes nozzles through which a liquid is discharged, are combined. For example, there is known a line-type ink-jet head in which the head units are arranged in a zigzag or staggered form in a main scanning direction (a width direction of a recording paper).
There is conventionally known a problem that jetting characteristics (an amount of liquid droplets to be discharged and jetting speed of the liquid droplets) of each nozzle change depending on variation in a physical property of the liquid caused by temperature change, such as the change of viscosity of the liquid. It is considered that the change of the liquid temperature is caused by variation in the temperature of an ambient environment, but a more severe problem occurs in a case that a drive unit for driving the head unit and a heating element such as a power unit are arranged in the vicinity of the head unit. In this case, there is fear that the heat radiated from the heating element at the time of driving the head unit increases the temperature of the liquid in the head unit and thereby changing the jetting characteristics of each nozzle greatly.
Meanwhile, for example, in a case that a printer performs printing for various kinds of paper having mutually different widths, instead of using all of the head units, only some of the head units are used depending on a condition such as a paper width, in some cases. Then, in the case that only some of the head units are used, in order to always maintain desired jetting characteristics, at least some of the head units, among the plurality of head units, which may be used by themselves, are desirably to be configured to have the least influence of the heat caused by the heating element.